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Math Help - Correct me if im wrong.. but

  1. #1
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    Correct me if im wrong.. but

    The function of  cos \pi/6  =  the cofunction of  sin \pi/6 or something similar... (forgot how it was worded)

    and would something like -2sin(4x)sin(-2x) be the same as 2sin(4x)sin(2x)
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  2. #2
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    Quote Originally Posted by 3deltat View Post
    The function of  cos \pi/6  =  the cofunction of  sin \pi/6 or something similar... (forgot how it was worded)

    and would something like -2sin(4x)sin(-2x) be the same as 2sin(4x)sin(2x)
    Sine and Cosine are Co-functions.
    Meaning,
    \sin x=\cos \left( \frac{\pi}{2} -x \right)
    In the same way,
    Tangent and Cotangent are cofunctions.
    And,
    Secant and Cosecant are cofunctions.

    You can use this mnemonic to remember the properties of trigonometric cofunctions.
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  3. #3
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    Sine and Cosine are Co-functions.
    Meaning,

    In the same way,
    Tangent and Cotangent are cofunctions.
    And,
    Secant and Cosecant are cofunctions.
    Ah. So the statement "The function of  cos \pi/6 Would = the cofunction of  sin \pi/6 ? =)
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  4. #4
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    Quote Originally Posted by 3deltat View Post
    Ah. So the statement "The function of  cos \pi/6 Would = the cofunction of  sin \pi/6 ? =)
    Thus, the by the cofunction identities,
    \cos \frac{\pi}{6}=\sin \left( \frac{\pi}{2} - \frac{\pi}{6} \right)=\sin \frac{\pi}{3}
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  5. #5
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    Quote Originally Posted by 3deltat View Post
    would something like -2sin(4x)sin(-2x) be the same as 2sin(4x)sin(2x)
    As sine is an odd function sin(-x) = -sin(x). Thus
    -2sin(4x)sin(-2x) = -2sin(4x) \cdot -sin(2x) = 2sin(4x)sin(2x).

    So the answer is yes.

    -Dan
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